This invention relates to apparatus for treating liquids and slurries by the use of a pulsed spark discharge between electrodes in a treatment vessel and, more particularly, to the purification of domestics, agricultural and industrial waters; sewage waste waters; industrial, chemical food processing and other toxic waste products; and the separation of dissolved sales and minerals, metals and other elements from liquids and slurries.
The increasing awareness of the need to treat liquid-like substances such as sewage, chemical and food-processing waste and other toxic waste products prior to their release into the surrounding environment has created a strong present interest in effective methods and apparatus for efficiently carrying out a purification process. One process described in U.S. Pat. No. 4,458,153 utilized the effects of a spark discharge produced between electrodes in combination with a localized magnetic field to alter the characteristics of confined liquid substances. Other investigations have resulted in limited volumes of liquid-waste being treated in a small confinement chamber, typically one liter or less, in which a spark discharge is established for a brief period. In this apparatus, a pair of electrodes are provided in the chamber with the pulsed energy from an external power source applied therebetween. The investigations have demonstrated that increased radiated power, shock waves and pressures in the vessel can be used to destroy micro-organisms in the liquid and effect purification thereof.
Results from spark discharge studies have been obtained using laboratory-size vessels to provide batch purification processing of small quantities of liquid waste. Primarily because of the energy requirements, the limited capacity of the treatment vessel and the use of batch treatment techniques, the spark discharge treatment method has not been commercially developed. Due consideration has not been given to the overall design of the confinement chamber so as to render it capable of use on a continuing basis for relatively large quantities of liquid waste. Furthermore, the energy consumption of known systems using a small confinement vessel is relatively large per unit of treated material. This characteristic is due in part to the lack of efficiency in the transfer of energy from the power source to the region between the exposed ends of the electrodes within the chamber.
In the confining vessel, the region between the electrode ends is the location of the spark discharge which generates the initial plasma channel. The transfer of energy to establish and expand the plasma channel is an important factor in generating the ultraviolet radiation, shock waves, electrohydraulic pressure and cavitation in the treatment vessel which produce the purification of the liquid waste. The amount of energy transferred to the plasma channel determines the amount of liquid waste that can be effectively treated in a single spark discharge for a particular designed chamber. Prior devices have been limited due to inefficient energy transfer and inadequate chamber design to the batch treatment of small quantities of liquid waste.
Accordingly, the present invention is directed to apparatus for treating liquid waste on a continuing basis wherein the efficiency of the energy transfer between power source and electrodes is improved. In addition, the treatment vessel of the apparatus is constructed to promote the effects produced by the spark discharge throughout the volume of liquid in the vessel. The combination of the features of the novel treatment vessel along with improvements in energy transfer permits treatment vessels of relatively large volume to be employed in the spark discharge treatment of liquid waste. Also, the present invention provides apparatus for continuing treatment of liquid waste without requiring lengthy interruptions in the movement of liquid waste material from a larger reservoir.